Posted
by
kdawson
on Tuesday February 17, 2009 @02:11AM
from the known-space dept.

goran72 sends in a story out of the Chicago AAAS meeting contending that Earth-like planets with life-sustaining conditions may be spinning around stars in our galactic neighborhood — we just haven't found them yet. "'So I think there is a very good chance that we will find some Earth-like planets within 10, 20 or 30 light years of the Sun,' astrophysicist [Alan Boss]... told his AAAS colleagues meeting here since Thursday. ... The images from those new planets, he added, should identify 'light from their atmosphere and tell us if they have perhaps methane and oxygen. That will be pretty strong proof they are not only habitable but actually are inhabited. I am not talking about a planet with intelligence on it. I simply say if you have a habitable world. ... Sitting there, with the right temperature with water for a billion years, something is going to come out of it. At least we will have microbes,' said Boss."

For the last 4 billion years the Earth has shed some 2 billion metric tons of genetic material per day. Solar winds have pressed some
of this material more, and some less. Some of this material has been captured by extrasolar objects and carried away. Some of it has been
captured by comets over which the sun no longer holds sway. Some of it has been so light and so thin that the solar winds have carried it
far from home.

The human body contains about 100g of DNA. You're saying about 2E15 grams, or 20 trillion human body's worth, of DNA is not only released into the atmosphere but then escapes the earths gravitational pull and enters interplanetary space.Sounds unlikely.

The human body contains about 100g of DNA. You're saying about 2E15 grams, or 20 trillion human body's worth, of DNA is not only released into the atmosphere but then escapes the earths gravitational pull and enters interplanetary space.Sounds unlikely.

That's because you didn't watch Stargate with as much enthusiasm as the OP obviously.

The human body contains about 100g of DNA. You're saying about 2E15 grams, or 20 trillion human body's worth, of DNA is not only released into the atmosphere but then escapes the earths gravitational pull and enters interplanetary space.Sounds unlikely.

Do you think we can get sued for that?*starts looking for a lawyer and holds on to his dead skin cells for a while longer*

Though I'm no expert, I do believe that worlds can pollute each other. Life is so incredibly contagious. Only one cell, or one bio molecule needs to survive. All kinds of events might blow some into the atmosphere and higher. Crashing asteroids and volcanoes might blast stuff into orbit.

For a planet to "shed" anything except perhaps hydrogen or helium, that stuff has to overcome escape velocity, which (until rockets were invented in the 20th century), requires an (volcano or meteorite) that would incinerate any complex organic compounds and render DNA a fine ash.

Plus, Google will tell you that the following comes out to 44%, as an above poster already said:

Less than 1% of Earth's mass is at a temperature that even permits life to exist. As for the part that actually consists of life, you can measure it in parts per million and still need scientific notation.

There have been spores tested, and the verdict is that they can survive at less than 10cm to an atomic explosion.

Citation needed.

A couple thousand degrees temperature will break up pretty much any chemical bond.

One atomic bomb can kill, at best, about 50000 people, in a dense city block less than 1 square kilometer.

Eh, what? Both of the bombs used in anger so far killed more than that (both directly by the blast and delayed deaths by radiation). And, mind you, those were small 10-15 kT devices. In todays strategic arsenals, you'll warheads ranging from a couple hundred kilotons to 1.2 megatons. And then of course, there's this little baby:

There are plenty of film clips that show the blasts of these things. However, there is never any scale to them. Either the blast is so far away that you can't possibly compare it to scenery or it is footage from high flying planes.

The chances of genetic material from the earth reaching other habitable planets is next to nil because:1) You are forgetting how astronomically tiny Earth is compared to...what is not Earth. Really not much material here.2) There aren't actually any known habitable worlds other than ours (doesn't mean they aren't there, just that they probably aren't prolific)3) The genetic material would be traveling so slowly compared to the distance to any planets out there that they might as well not even be moving.

This sounds unlikely. The mass of the Earth is about 6 x 10^24 kg. If Earth is losing 2 x 10^12 kg of material every day then the Earth would lose all of its mass in about eight billion years, and this assumes that all of the material being lost is the genetic material.

Yes, the accretion rate should be included too. A quick Google gives a terrestrial accretion rate of about 4 x 10^7 kg/year at present. That is about 0.01% of the claimed rate of loss of genetic material, which is not enough to save the Earth from blowing away in the Solar wind. The number in the original post just does not add up.

Lately I've been really pessimistic about the whole thing, I mean, really, who cares? Even if there were intelligent life on planets that close, we would only be able to exchange communication once every 10 years, not enough to actually learn their language, and we would never be able to travel to visit them, right?

So realistically, there is not much point except for dreamers and space geeks. Might as well spend the effort here on earth. On the other hand, what if we could travel out there? Wouldn't it be COOL? I might actually meet a girl. Just kidding.

I want to believe that we will be able to travel long distances one day, hyper speed and all that, but it's pretty hard to see how it could happen.

We could give them, say, the entirety of Wikipedia, and they could give us their equivalent. Write up a "rosetta stone" with a bunch of pictorial/mathematical representations of words, and so on. Probably doable. Conversation back and forth will seem frustratingly slow, but there's no limit to the amount of info that can be streamed across. Mind you the chances that we will be in the near vicinity of a civilization that communicates by radio waves that we can pick up is possibly quite slim- we've only been doing it for less than a hundred years. They could be in our equivalent of 1750 and we'd never hear a peep.

While technically it is no problem to send them large quantities of information, local law prohibits most of it and you will be sued by different interest groups if you try. So if we find someone out there, then we will probably start to spam them with viagra adds..

So what we can conclude as likely is that no civilization within around fifty light-years is advanced enough to detect our radio signals and respond....

Well, either that or they're advanced enough to have detected them, but not advanced enough for FTL travel, and they didn't want to respond via radio. Because if you saw Barney the purple dinosaur and Rush Limbaugh on TV, would you want to give us any warning you're coming before you nuke us from orbit?

Or they were advanced enough at some point and have since bombed themselves back into the bronze age and are building themselves back up again. We really have no data about how stable a technological society is, if it turns out to be a hundred years of advanced technology for every 10,000 of savagry, it would be quite fortuitous to exactly line up with a suitable conversation partner.

"In Italy for 30 years under the Borgias they had warfare, terror, murder, and bloodshed, but they produced Michelangelo, Leonardo da Vinci, and the Renaissance. In Switzerland they had brotherly love - they had 500 years of democracy and peace, and what did that produce? The cuckoo clock."

It's worse than this. The Earth has existed for 4.5 billion years and contained a civilization that could reasonable detect radio waves for a little over a 100 years. Thus, the chance of a given Earth-like world having a civilization with roughly 20th century technology is about 45 million to 1.

Even if the average civilization lasts a million years, the odds are still 45,000 to 1 that any particular Earth-like world will contain one. The chance of us finding a civilization that inhabits a single nearby E

In a universe with an age measured in billions of years, it might be just as likely the separation in advancement of species be measured in millions of years. i.e., "they" could be far, far off being able to communicate, or advanced enough that them buzzing our planet and abducting people to study could be done without causing a massive fuss (outside of what many would think of as crazies talking about a close encounter).

In fact, they could be our equivalent of 2009 and we'd never hear a peep.

Except for one or two exceptions, no radio signals from Earth are strong enough to be detectable at interstellar distances using the receiving technologies that we use for SETI.

The "exception" is ballistic-missile warning radar, which might be detectable, if it were at the wavelength being searched, and they happened to be looking in the right direction when the Earth happened to be rotated so that the radar pointed the right way. B

Mind you the chances that we will be in the near vicinity of a civilization that communicates by radio waves that we can pick up is possibly quite slim- we've only been doing it for less than a hundred years.

And how much longer are we going to be doing it, with everything converging onto the Internet? If the earth lights up as a radio source in the early 20th century, but has gone dark again by the dawn of the 22nd because almost everything is now connected to fibre, what hope is there for SETI?

Write up a "rosetta stone" with a bunch of pictorial/mathematical representations of words, and so on. Probably doable.

I know a lot of science fiction books and music like to tout math as a "universal language" but it's really not a language at all. In fact, we need language in order to convey the mathematical concepts.

Case in point, most human scientists had difficulty deciphering the Pioneer plaque [wikipedia.org] and it's attempt to encode information about humans and the location of the earth in a mathematical way. A lot of the things we don't think of as "language" such as arrows to point directions, really are.

I would think that we wouldn't just send "Hi" and wait for a response. I think we would constantly be sending them information and let them learn what we are sending. We would hope they would do something similar.

Lately I've been really pessimistic about the whole thing, I mean, really, who cares? Even if there were intelligent life on planets that close, we would only be able to exchange communication once every 10 years, not enough to actually learn their language, and we would never be able to travel to visit them, right?

So realistically, there is not much point except for dreamers and space geeks. Might as well spend the effort here on earth. On the other hand, what if we could travel out there? Wouldn't it be COOL? I might actually meet a girl. Just kidding.

I want to believe that we will be able to travel long distances one day, hyper speed and all that, but it's pretty hard to see how it could happen.

Firstly, it's "warp speed" not "hyper speed", and secondly, you weren't kidding - keep trying with the terrestrial women for now. I admire your spirit kid, but you're no James Tiberius Kirk.

There have been several of these stories in the last month or so. Enough to make one suspect that someone has an agenda.
It's all fantasy and dreaming until there's some hard evidence. For all the theories for there being intelligent life Out There, there are as many that run against it.
The simple fact is we don't know and, apart from a desire to find something, we have no reason to suspect that there is life beyond this planet.
So far we have one life-bearing planet in this solar system. The others we'v

This is modded insightful? "For all the theories for there being intelligent life Out There, there are as many that run against it." Sounds like what Creationists call an 'argument' against evolution. Nothing but the vague implication that some kind of opposing view exists somewhere. I for one would really like to hear some of these theories against extraterrestrial life. While I won't turn to the Drake Equation, I'll just say how in the hell do you expect that out of a trillion or so stars in our galaxy al

No reason to suspect? It goes like this. There is life on this planet. Therefore probability of life > 0. There are many, many, many stars in our galaxy, countless in the universe. No matter how small the chances are, given the size of the universe and since we have proven that the probability is greater than 0, it's inconceivable to imagine that we're the only ones.

In fact, the only reason to be arrogant enough to say that we're the only ones would be religious nonsense.

Actually, it's more like "one is one, two is many". Until we have some kind of proof of life beyond this planet, the reasonable assumption is that life is peculiar to this planet. Sure, from what we know of how life on this planet developed, it seems reasonable that we're not special. However, we don't even see it in other "reasonable" places in our own solar system. It's not evident on Mars, even though certain earth-like bacteria could probably thrive there. It's not evident on Venus, which despite

Sure, from what we know of how life on this planet developed, it seems reasonable that we're not special. However, we don't even see it in other "reasonable" places in our own solar system.

It has nothing to do with what we know of how life on this planet developed. It just means that unless you assume development of life requires conscious divine intervention, it happened as a result of certain conditions. We could be very special in the sense of life being an extremely low probability, even given the right conditions. However, given the size and age of the universe, it doesn't matter how low the probability is: if it happened once, it's happened multiple times.

Just curious, how exactly would microbial life on Venus, Mars or any other object in our star system be evident? Microbes aren't exactly known for building large cities and transmitting radio waves. Mars is the only one we've sent a biological testing station to and it was only able to test a few samples from a very limited area.

I think the biggest limitation most people put on the idea of life elsewhere in the universe is that people always assume all life is carbon-based like us. There's no reason to b

Lately I've been really pessimistic about the whole thing, I mean, really, who cares? Even if there were intelligent life on planets that close, we would only be able to exchange communication once every 10 years, not enough to actually learn their language, and we would never be able to travel to visit them, right?

I wouldn't be so pessimistic. Sure, conversations would have multi-year latency, but so what? I mean, I don't communicate with Japan, but I still find their cartoons hilarious. Some people in

Lately I've been really pessimistic about the whole thing, I mean, really, who cares? Even if there were intelligent life on planets that close, we would only be able to exchange communication once every 10 years, not enough to actually learn their language, and we would never be able to travel to visit them, right?

I wouldn't be so pessimistic. Sure, conversations would have multi-year latency, but so what? I mean, I don't communicate with Japan, but I still find their cartoons hilarious. Some people in Japan watch American TV and enjoy it, even if they never contact the producer to tell them as much. Once contact is established between two civilisations, you'd have constant data being sent back and forth. It's impossible to say if we'd figure out a language, but it'd still be interesting just to see what they put out there for the universe to see.

And, honestly, I feel that language would be pretty doable, if you get something like TV established. It might be impossible if all we ever get is radio, so we can never see a context for their words, but if we can get something like "Barney" for aliens, we'd probably be able to sort out some of what they are saying.

Sooo....we'd get to watch alien television.
Some where out there...there's a planet of cat girls working hard to finish a animated series about squishy pink aliens who call themselves geeks.

Once it became known that a civilization existed in a particular star system... and they knew about us... communication could be continuous both ways, not just back-and-forth like a walkie talkie every 10 years.

Starting with math: primary numbers, Fibonnacci sequence and other natural patterns, on to addition, subtraction, etc... then to logical propositions and conclusions... we could communicate an entire language and maybe even a couple of encyclopedias in the time it took for ONE 10-year round trip of communication.

And with ion drives, or Bussard ramjets (especially if they are Pellegrino-style vehicles that pull instead of push), maybe we could get there in, say, 50 years or so. And spend most of that time in something like cold sleep. There have been advances in that direction, too. Do we have the technology to do this? No. But we might in 10 years, or 20.

Of course, we would have to decide what and how much to send in our communications. There could be very real danger. I do not think most people understand just how deadly we (and by implication, they) could be, given enough time and effort, even to a civilization light-years away.

"Flying to Valhalla", by Charles Pellegrino, is a work of fiction. It is the book in which he introduced a totally new (but perfectly sound from an engineering standpoint) style of interstellar ship construction. As controversial as Pellegrino is as a person, there is no doubt that he is, as the saying goes, "wicked smart". There are some very plausible cautions in his book.

There are 6.75 billion people on Earth. We will have no trouble finding enough who are (a) qualified and (b) want with all their hearts to volunteer for a one-way trip. (There would be quite a bit of attrition over 50 years, but 30 would be very doable.)

We will have much more trouble convincing people to fund the project than finding volunteers.

Starting with math: primary numbers, Fibonnacci sequence and other natural patterns, on to addition, subtraction, etc... then to logical propositions and conclusions... we could communicate an entire language and maybe even a couple of encyclopedias in the time it took for ONE 10-year round trip of communication.

Agreed. Communication does not always have to be unidirectional. There's no good reason why we couldn't both be sending and receiving at the same time.

And with ion drives, or Bussard ramjets (especially if they are Pellegrino-style vehicles that pull instead of push), maybe we could get there in, say, 50 years or so. And spend most of that time in something like cold sleep. There have been advances in that direction, too. Do we have the technology to do this? No. But we might in 10 years, or 20.

That's a bit optimistic. Make that ~500 and ~200 years and I'll agree with you.

Any technology capable of crossing the distance between stars could be enormously dangerous. Take a ship weighing ~100 tons for example. At.1c it could hit the earth with more than enough energy to end civilization.

Just the engine exhaust alone would be a hot plasma plume thousands of kilometers long at least. That's quite enough to create a global EMP among other things.

As the other responder noted: even a very small mass, traveling at a sufficient fraction of C, could be a planet-buster.

But the real issue here is that we do have the technology to do that. All it would take is a vast amount of effort and resources to build and fuel a vehicle capable of driving that mass to a sufficient velocity. We have the tracking and navigational technology. All it would take is a massive effort.

And the really nasty part is, once traveling at an appreciable fraction of C, by the t

I honestly am not convinced that we'd need any brand new branch of physics to send someone to a star 10 lightyears away. When you start accelerating to high speeds, time dilation comes for free with the package. I remember someone showing me the math a while ago, but I don't remember who it was so they may have been full of it, but anyways... for traveling large distances under constant acceleration you can pretty much use classic Newtonian physics from the point of view of the traveler, as reaching relativistic speeds causes space to constrict rather than time if you are the traveler rather than the stationary observer.

What does this mean for traveling interstellar distances? If you can carry enough reaction mass or somehow collect it on the way, simply accelerate at a comfortable rate until you are halfway to the destination, then turn around and begin deceleration at the same rate for the second half. working the numbers [google.com] shows that accelerating at 9.8 meters per second per second will get you halfway to a destination 10 light years away in 2.2 years. 4.4 year one way trip, 8.8 year round trip. All with 1G of acceleration so you would have no need for exotic technology to simulate gravity to maintain health. There would physiologically be no need for sleep/stasis for the travelers. Stasis may, however, prove to be more energy efficient and psychologically easier than being cooped up in a spaceship for about 9 years.

Granted, the relativistic effects would need to be taken into account for plotting the course, as the destination planet will have been traveling through space for much more than 10 years. And when you get home your descendants will probably have died of old age.

I think it'd pretty much have to be a one-way trip. Sending people 10 lightyears through space isn't cheap. The only reason to send people there in the first place would be either to act as ambassadors and advisers to the intelligent species living there, or to set up a colony if the planet happens to be devoid of intelligent life. Either way, coming back wouldn't be part of the plan. The ship could be put to much better use such as ferrying things back to earth, whether they be alien ambassadors or phy

...shows that accelerating at 9.8 meters per second per second will get you halfway to a destination 10 light years away in 2.2 years. 4.4 year one way trip, 8.8 year round trip

Uh-huh. You want to continuously accelerate at 1G for 2.2 years (and then presumably decelerate at 1G for the remaining 2.2 years). Care the calculate the amount of fuel you'd need for that? The amount of food you need to carry to sustain a crew for 4.4 years (we'll assume we can refuel and restock at the planet we're going to)?

If you can carry enough reaction mass or somehow collect it on the way

Yeah, see...you've concentrated on the relativistic issues and brushed off the real problem. Time to get there isn't a problem. Even if it took 500 years, if we assume we can c

Ah yes... good point that I really should have clarified. I wasn't intending to prove that it is technologically realistic to travel this fast, more that it wouldn't break the major laws of physics (namely the laws of thermodynamics, which I believe "actually" traveling at the speed of light would violate.) Finding a way to maintain this acceleration would indeed be a huge feat of engineering on a scale likely orders of magnitude from what we can currently obtain. But that doesn't necessarily mean that i

I wasn't intending to prove that it is technologically realistic to travel this fast, more that it wouldn't break the major laws of physics...Finding a way to maintain this acceleration would indeed be a huge feat of engineering on a scale likely orders of magnitude from what we can currently obtain. But that doesn't necessarily mean that it is impossible.

Ah. In that case you are absolutely correct. Thanks for clarifying your point for me.

While it initially appears that you would be traveling faster than the speed of light, you indeed are not... when you reach relativistic speeds space itself compresses, so from your perspective the distance traveled between two points is less than the distance as measured from a resting observer. End result your measured velocity is less than C. To the resting observer, you travel the larger distance, but time is dilated such that your velocity is lower than C. Since the apparent distance between the origin and the destination is decreased, the amount of time it takes light to make the same journey would be less than the amount of time it takes you. In fact, from your perspective light is still traveling... at the speed of light.

Now, to take the concept to the ultimate (but unreachable) conclusion: to reach such a velocity that an outside observer would record you as moving equal to the speed of light: To the traveler it would seem as if there was actually no distance traveled, and the journey took no time at all. What the traveler would observe is space and time folded between the origin and the destination... for a 10 light year journey, you would instantly travel to the destination, but 10 years later. The return trip would also be instantaneous, but 20 years would have elapsed at home since you have left. Thus, the speed of light is not violated. However, to cut your travel time to zero in a Newtonian framework, you would need to reach infinite speed in zero time, which would require infinite acceleration, which would in turn require infinite energy. That is impossible, so an object with a resting mass cannot travel at the speed of light (or beyond.) But you still have to take into account the fact that at relativistic speeds, space constricts while time dilates, allowing for what on the surface appears to be traveling faster than the speed of light, but actually is not.

There was a Sci Fi short story about this (I think it was Asimov). Basically, a mission to one of the moons of Saturn found life, but the space ship was going to be destroyed in a couple days. The question was how to get as many questions answered in that time period as possible.

The scientists were trying to figure out a faster-than-light communication technique. The answer of course, was more mundane. Continuously send and receive information. If something to you garbled, ask to it to b

> Lately I've been really pessimistic about the whole thing, I mean, really, who cares? Even if there were intelligent life on planets that close, we would only be able to exchange communication once every 10 years, not enough to actually learn their language, and we would never be able to travel to visit them, right?

Not really. The idea of radio communications with light-years distant targets has been discussed at least as far back as the forties. The idea is, you just keep talking -- send any data

The difference being, of course, that the tools exist to let you find out whether the treasure chest is there if you choose to do so. That isn't the case yet for finding Earth-size planets 10 or 20 light years away, especially if they're orbiting a long way out from a bigger, hotter star than ours.

In any case, it's considerably more likely that somebody made a few bucks by accepting barrels of toxic waste for burial in what is now your back yard, then sold the property to a developer.

The difference being, of course, that the tools exist to let you find out whether the treasure chest is there if you choose to do so. That isn't the case yet for finding Earth-size planets 10 or 20 light years away, especially if they're orbiting a long way out from a bigger, hotter star than ours.

In any case, it's considerably more likely that somebody made a few bucks by accepting barrels of toxic waste for burial in what is now your back yard, then sold the property to a developer.

Yes but if you can prove it and sue it's just as good as a treasure chest.

'I simply say if you have a habitable world.... Sitting there, with the right temperature with water for a billion years, something is going to come out of it. At least we will have microbes,' said Boss.

Water is definitely a necessary component to our form of life, however a stagnant pool of water won't produce even microbes in any prompt fashion on a cosmic scale. The moon is as big a contributor to life on Earth as its water, because of how the tide has stirred the water like no other planet we've dis

The moon is as big a contributor to life on Earth as its water, because of how the tide has stirred the water like no other planet we've discovered yet.

That's complete woo-woo. There's absolutely no reason to believe that the moon had any effect on the emergence of life. It's a fun little theory if you're the kind of person who likes abstract art, but it's certainly not supported by any scientific evidence.

however a stagnant pool of water won't produce even microbes in any prompt fashion on a cosmic scale. The moon is as big a contributor to life on Earth as its water, because of how the tide has stirred the water like no other planet we've discovered yet.

Obviously you are unfamiliar with the concept of thermal turnover.

No tide is necessary to mix a body of water. All you need is rotation.

Gotta stop farting around with pointless space station projects that are due to be retired just after they're finished and build a real space SHIP. Oh, but thanks to friggin' Carter and now Obama, we can't make better use of nukes. Smooth move, ex lax.

We have the technology today to explore our closest neighbors. We just lack a long-term vision and plan to make it happen and fund it indefinitely.

We've already proven the ability to observe from afar, both from a terrestrial setting and via space-bound satellites or probes. We have also proven the ability to launch deep-space probes for extended operation. We need to put the pieces together to establish an ongoing and expanding network of observational probes and relay satellites.

French scientists have discovered the smallest planet yet located out of our solar system, a celestial find less than twice the size of Earth and which orbits a Sun-like star.

That's with the technology we've got in operation now (also referenced in TFA). In the next decade we're set to put up even better technology [wikipedia.org]. You can bet that if Earth-like habitable planets are at all common in our neck of the woods we'll have found one within the decade.

As I've posted before, this type of "Earth exceptionalism" is more related to the field of religion than science. There is no a priori reason to believe that the Earth is an unusual planet unless you buy in to the creation myths of some peoples who lived in the Near East circa 4000-2000 years ago. (Other societies, such as those of India, believed in a plurality of worlds and intelligent life forms.) Using Occam's Razor we would conclude that our planet revolves around a very ordinary star, everything else observed about our planet suggests it is unexceptional, therefore the emergence of life is likely to be unexceptional. Falsification of the default hypothesis would involve finding an earth-like or near earth-like planet which did not have life on it. Protestant Biblical literalism is not a scientific attitude. So far, the history of science has shown that every form in which exceptionalism has shown up has been found to be wrong, e.g.

This is why bigotry towards the religious is so important - it puts them in their place. We need to replace religion with 100% science - superstition is no way to go through life. It's our responsibililty to stamp out religion wherever it appears.

I agree completely! Even worse are those Elvis-is-not-still-alive loonies! Fine, I say, prove it. show me your documented research on the subject, using whatever methodology you wish, that establishes, scientifically/logically/whatever, that elvis isn't alive. oh, you mean you accept it on FAITH that he isn't alive?....

Interesting...one little teenie tiny problem though; it can be proven scientifically that Elvis is dead through forensic examination.

What??? YOU'RE ONE OF THEM??? And here I thought you were a rational person and a critical thinker! How can you say something so stupid?

Everyone knows that the body they put in the ground wasn't really Elvis, and the forensic evidence they kept wasn't him either! Besides, since Elvis is all powerful, he could remotely modify the results of their test! So your "science" co

Extremely unlikely is fine. I have no problem with extremely unlikely. I just get tired of the Dane Cook styled atheists who treat anyone who admits to a religion as if they were fools or retarded.The stone hitting the floor thing is mainly used as part of a safety lecture; "will this rock hit the floor if I drop it?" "yeah, of course". I drop it with one hand and catch it with the other. to make a long story short, you can't count on ANYTHING in a uncontrolled environment.regardless, I maintain that you h

There is nothing religious about the "Earth exceptionalism" theory of having a close orbiting moon roughly half the mass of the planet. I just finished writing another post in this thread explaining it [slashdot.org].

Using Occam's Razor we would conclude that our planet revolves around a very ordinary star, everything else observed about our planet suggests it is unexceptional, therefore the emergence of life is likely to be unexceptional.

We don't have enough data to draw any meaningful conclusions. The list of known Earth-like planets is extremely short (one might even say, nonexistant). Therefore, trying to assert _anything_ about whether the Earth is "ordinary" or not is, by definition, pure speculation.

As I've posted before, this type of "Earth exceptionalism" is more related to the field of religion than science. There is no a priori reason to believe that the Earth is an unusual planet unless you buy in to the creation myths of some peoples who lived in the Near East circa 4000-2000 years ago.

That said, even if earth is a common type of planet, there is strong evidence that intelligent life is rare simply because evolution tends to favor lifeforms such as the dinosaurs or bacteria.